The invention relates to an oil cooled reciprocating internal combustion engines with free standing cylinders and low emission of heat, sound and harmful substances.
The equation cooling equals heating must apply for all combustion engines. However, what is expected from a future engine is that the emission of heat should be as low as possible. In addition, unavoidable heat losses should be utilized, at a maximum possible heat level, for useful purposes, such as e.g., cabin heating. Since cooling water boils at a relatively low temperature and cooling air cannot be used for numerous purposes as a result of its contamination by the engine, it is desirable to utilize engine oil as a cooling medium. For this reason, there were numerous attempts to provide engine parts, such as pistons, cylinders and cylinder heads, with oil chambers in order to intercept the developing heat (e.g., German Pat. No. 26 49 562).
For reasons which are attributable to the thermal characteristics of oil, the equation heating equals cooling applies only in the case of low heating action, i.e., small engine output.
Substantially higher engine outputs with pure oil cooling are achieved when the piston and the combustion process are selected in such a way that only little heat can pass from the combustion chamber to the cylinder wall (German Pat. No. 33 14 543). However, here again there exists a limit as to the capacity of such oil cooling in that the cooling action is effective substantially only transversely of the crankshaft. Such cooling is not effective in the direction of longitudinal section of the engine because the deflecting vanes for cooling oil which are disposed in the lower portion of the piston act in a single direction. Thus, the internal cooling is not uniformly distributed along the periphery. The external cooling, too, is not effective along the entire periphery of the cylinder because each of the cylinders constitutes a one-piece casting. Such construction exhibits internal as well as external cooling defects, as considered in the longitudinal direction of the crankshaft.